I´ve ridden from Santiago -- actually, BA to begin with -- as far north as Cali though, thankfully not all at once. A week of travel, at least, and as you might expect, not all that pleasant. You´d need to break up the trip in order to keep from going insane, and I would suggest taking absolutely the best class of bus you can afford on each leg to make the trip bearable. If you´re taking the bus to travel, or to make a point, that´s one thing. But if you simply need to get from Bogota to Santiago, and you aren´t overburdened with luggage, I´d look into a flight. You won´t save that much by taking a bus (a decent bus from Chile to Arica is at least 100 usd, for example), and large stretches of the trip -- particularly through Chile and in Peru between Arequipa and Lima -- are pretty uninspiring. Buena suerte.